Body organs display complex shapes, surfaces and internal structures, including blood vessels. Coupled to morphological complexity, the component tissues of organs possess dynamic contractile and mechanically responsive elements such as sphincter muscles. The ability to accurately recapitulate naturally occurring complexities of shape, internal structure and functionality is a key goal of tissue engineering. Current approaches to this problem include the use of scaffolds to generate in vivo like environments for cell growth or “organ printing” where point-by-point extrusion from a modified ink-jet printer has enabled cells to be precisely arranged into three-dimensional tissue-like structures.
Technologies based on culture scaffolds or organ printing rely on application of straightforward engineering principles. To date, the field has been less successful in harnessing self-organizing processes occurring during embryonic development to elaborate useful biological structure in vitro.
Similarly, a tissue-engineered approach for wound healing attempts to promote regenerative and scar-free healing. In this regard, stem cells are increasingly being utilized as part of regenerative therapies. To date, conventional regenerative therapies based on stem cells involve the introduction of dispersed cells into a diseased organ with little regard for the status of these randomly introduced cells. Current therapies often show marginal, variable, or even controversial propensity to promote regenerative and scar free healing. As such, improvements to available compositions and methods would be beneficial.
The epithelial-mesenchymal transition (EMT) precedes virtually every cellular differentiation in the embryo. For example, during human development one of the first rounds of EMT occurs as part of gastrulation, in which the 3 embryonic germ layers differentiate. Subsequent rounds of EMT within germ layers occur as a prelude to morphogenetic processes as diverse as neurogenesis, myogenesis, and vasculogenesis.
The precise role of EMT is unclear. EMT resembles a priming step that precedes morphogenetic events. Progenitor (i.e., stem) cells form stable cell-cell junctional contacts, synchronizing cytoskeletal organization, polarity, and to some extent proliferative activity. The cells then detach, transforming into invasive mesenchymal cells in a coordinated progression toward terminal differentiation.
The present disclosure describes a unique and non-obvious series of steps to stimulate an EMT-like state in cells in a culture dish (referred to as EMT-priming or activation) to provide: a) microtissue compositions (e.g., toroids of EMT-primed/activated cells) with medical uses in tissue engineering and b) regenerative healing methods and compositions as described in the subsequent text of this disclosure.